An optical fiber encased in a metal sheath which compresses an intermediate layer of material surrounding the optical fiber is known, as shown by the following two patents.
Thus, U.S. Pat. No. 4,214,693 discloses a stranded conductor surrounded by electrical insulating material which in turn is surrounded by a metal sheath. The conductor may be stranded copper, or one or more of the conductors may be strands of a material suitable for practice of "fiber optics", typically glass fibers or coated glass fibers. According to the patent's disclosure, the "fiber optics" material may be used alone, without any metal conductors. The insulating material may be a thermoplastic material such as polytetrafluoroethylene, or a fully fluorinated copolymer of hexafluoropropylene and tetrafluoroethylene, or propylene polymers and copolymers. Where "fiber optics" material is used, the amount of other insulating material required is reduced, and may, in some cases, be entirely eliminated. The metal sheath is preferably made of stainless steel and is swaged. The end product is a wireline utilized to suspend a downhole tool in an earth borehole from an aboveground cable drum, and to transmit signals between such tool and above ground-equipment.
U.S. Pat. No. 4,381,141 discloses an optical fiber produced by preparing a preform of a core and clad both made of metal halogenides or arsenic-selenium glass, applying a lubricant to the outer surface of the preform, vacuum sealing the preform within a metal pipe, made of copper or aluminum, and drawing the metal pipe through a die at a temperature below the melting point of the preform, to reduce diameter and elongate. The lubricant may be a fluorine type resin, a fluorine type polyolefin, a polyolefin polymer such as polyethylene or boron nitrides.